Piper Alpha
High Pressure/High Temperature (HPHT) drilling has long since been considered as a very dangerous, but necessary drilling method. HPHT drilling is used specifically in instances when the earth’s surface needs to be deeply penetrated. An example of this would be the off-shore drilling platforms that produce oil in the North Sea.
In 1988 the Piper Alpha platform fell victim to one of the risks of HPHT drilling – explosion and fire. This incident was the worst oil rig disaster in history. The death toll of this incident was 167 (including two crewmen from a rescue boat) and only 62 people survived.
The following timeline illustrates the problems with the HPHT drilling and pumping systems:
On 6th July 1988 at approximately 12:00 Pump A’s safety valve was removed for routine maintenance. A flat metal disc was placed in the resulting opening and a notice was issued that the pump should not be started or used under any circumstances.
When the night shift started at 18:00 this notice was placed in the control room without anybody’s attention being drawn to it. This permit disappeared and was never seen again. There was another notice for the pump’s overhaul which had not yet begun. This was kept in a different location.
21:45: Pump B stopped unexpectedly and refused to restart. It was essential that the pump be restarted immediately or else the platform would lose its power supply. After searching for a permit stating that pump A could not be restarted – and finding none – the decision was made at 21:52 to start pump A. Nobody noticed the flat disc covering the opening for the safety valve. At 21:55 the pump was started and the metal disc failed, allowing gas to escape under high pressure. The gas then ignited and exploded.
By 22:04 everybody had abandoned the control room and emergency instructions were no longer being given out. Crewmen were trying to make their way to the lifeboat deck, but were prevented by the fire and gas explosions. The fire, smoke and the wind prevented rescue helicopters from landing and the fire control systems had also failed. In a desperate attempt two men put on fire retardant clothing to go below deck and try to start the fire control systems. They were never seen again.
Unfortunately production from two other platforms were not stopped and kept on pumping pressurised gas to Piper Alpha, feeding the fire and causing more gas explosions. After the second major explosion both platforms shut down, but the decision was too late. Piper Alpha was engulfed in fire and disappeared into the sea.
The Piper Alpha disaster was an expensive lesson (in money and lives) to learn about HPHT drilling.